Figure 5.
The aromatic AA F78 functions in combination with the upstream AA as a gate for the long closed time. Characteristic single channel fluctuations of mutant KcvS F78A (a) and KcvNTS G77S F78A (b) at ±120 mV in planar lipid bilayers. (c) Mean single channel i/V relations (±sd) of KcvNTS (open squares), KcvS (filled squares), KcvS F78A (orange circles, n = 4) and KcvNTS G77S F78A (blue circles, n = 7). (d) Mean open probabilities (±sd) of wt channels and mutants (n = 4 and n = 7 for KcvS F78A and KcvNTS G77S F78A, respectively). Exemplary closed dwell times at +120 mV for KcvS F78A (e) and KcvNTS G77S F78A (f). The data in e and f can now be fitted with two exponentials. Radar plots for probabilities (P) of the wt channels and mutants for occupying the open state (O) and the closed states (C1–C3) (g) and for mean lifetimes (in ms) of the open state (τo) and of the three closed states (τc1–τc3) (h). The mean lifetimes were calculated from three independent 5 min recordings. The symbols in d, g and h correspond to those in c.